Use Android’s built-in App Pinning feature
Go to Settings > Security or Security & privacy > App pinning
Turn on App pinning
Open the app you want to lock
Open Recent Apps
Tap the app icon and select Pin
To unpin, use the required gesture or PIN/password
Use a third-party app locker from Google Play Store
Install a trusted app lock app
Grant required permissions such as Accessibility or Usage Access
Select the apps you want to lock
Set a PIN, pattern, or password
Enable fingerprint or face unlock if supported
Use Samsung Secure Folder if you have a Samsung device
Add the app to Secure Folder
Open the app only from Secure Folder
Use Xiaomi App Lock if available on your device
Go to Settings > Apps > App lock
Choose the app and set a lock method
Use built-in device-specific app lock features if your phone supports them
Set a strong device screen lock first
Keep your phone software updated
Avoid granting permissions to untrusted app lockers